Overview

An operating system acts as an intermediary between the user of a com- puter and the computer hardware. The purpose of an operating system is to provide an environment in which a user can execute programs in a convenient and efficient manner.

An operating system is software that manages the computer hard- ware. The hardwaremust provide appropriatemechanisms to ensure the correct operation of the computer system and to prevent programs from interfering with the proper operation of the system.

Internally, operating systems vary greatly in their makeup, since they are organized along many different lines. The design of a new operating system is a major task, and it is important that the goals of the system be well defined before the design begins.

Because an operating system is large and complex, it must be cre- ated piece by piece. Each of these pieces should be a well-delineated portion of the system, with carefully defined inputs, outputs, and func- tions.